Geez, you're on hot water radiators? Where do you live? If its your house, convert to central heat/air. If not, call your landlord and get him to correct it.

radiant heaters r one of the cleanest most efficient ways to heat a home. Maybe because u associate them with old houses u think they are out dated. Maybe outdated fashion wise for some but not outdated efficiency wise.

Switch or valve is probably on regardless of what the knob is telling you. The knob could be broken and just turning with no effect.Another thing could be that the valve is just leaking.

Trying to think who you could call for something like this.... maybe a local hvac company or as odd as it sounds , a plumbing company. Or you can try to mess Around with it yourself, but I'm sure you've already tried that.

The plastic knob is probably reamed out and isn't grabbing the valve stem. I'd try to remove the plastic knob to expose the stem and see if you can operate the valve with pliers, vice grips, wrench, etc. Then you'll know if you need an entirely new valve or just a stem key.

Take care not to fuck up the stem by turning it with a loose fitting wrench and shearing off the corners. If it's fighting you, don't force it or you could create a much bigger problem.

Don't continue to force the plastic cap off to one side with shims in an effort to get purchase. This will stress the stem and packings and may cause a leak.

I think Diablo Blanco is a heating/plumbing guy so maybe you two can get together and talk about hairy ass cracks.

radiant heaters r one of the cleanest most efficient ways to heat a home. Maybe because u associate them with old houses u think they are out dated. Maybe outdated fashion wise for some but not outdated efficiency wise.

they require a oil/fioul/fuel furnace to work most of the time in old buildings/houses...not effective at all especially considering the coming oil shortages/high prices. Nothing is cheaper than a modern efficient furnace that uses heating wood and / or electrical baseboard heating . Pulsed hot air when it works with electricity is average economically speaking (fan consumes a lot of electricity so do the diodes), when its oil again it s shitty; consume tons of energy to make that huge fan turn and oil is getting expensive. Also house/flat insulation /isolation are important and work hand in hand with heating system.; you have to have good quality windows and ventilation systems.

they require a oil/fioul/fuel furnace to work most of the time in old buildings/houses...not effective at all especially considering the coming oil shortages/high prices. Nothing is cheaper than a modern efficient furnace that uses heating wood and / or electricity. Pulsed hot air when it works with electricity is average, when its oil it s shitty; consume tons of energy to make that huge fan turn. Also house/flat insulation /isolation are important and work hand in hand with heating system.; you have to have good quality windows and ventilation systems.

Electric heat is the most inefficient by far. Natural Gas is the best in my opinion.

The plastic knob is probably reamed out and isn't grabbing the valve stem. I'd try to remove the plastic knob to expose the stem and see if you can operate the valve with pliers, vice grips, wrench, etc. Then you'll know if you need an entirely new valve or just a stem key.

Take care not to fuck up the stem by turning it with a loose fitting wrench and shearing off the corners. If it's fighting you, don't force it or you could create a much bigger problem.

Don't continue to force the plastic cap off to one side with shims in an effort to get purchase. This will stress the stem and packings and may cause a leak.

I think Diablo Blanco is a heating/plumbing guy so maybe you two can get together and talk about hairy ass cracks.

1st would be just remove the green shims from under the white plastic cap, then turn the cap to close the valve. I'm guessing the cap will turn fairly easily without having any effect on the valve's operation. If that's the case you can then remove the cap to expose the stem and test the valve's operation with vice grips.

If the cap is really loose it might pull off quite easily. You won't get any water coming out because the cap is only there to turn the stem and doesn't act as any kind of seal. As far as I know. Lol.

If I guessed right you're going to end up having to rig some sort of new cap/stem key, or just keep using a wrench or grips on it. If you're not into that it might be easier to do as the other guy suggested and just replace the valve as a unit. Some photos and measurements and a local plumbing shop will probably sell you one for $15? or so. Presumably dimensions and threads are standard if Powerlift got his valves online, but that would make me a little nervous without checking the specs.